Combine condensed milk, butter, powdered sugar and egg yolk in a bowl and beat with a mixer on low until light and fluffy. Add flour and almond flour to the butter mixture, beating until the flours are absorbed. Add almond extract and beat well to incorporate.
Lay a sheet of plastic wrap and turn the dough out onto it. Gather the dough into a ball, press into a thick disk, and wrap it well. Refrigerate for 30 minutes.
Preheat oven to 325 F. Line a baking sheet with parchment paper.
On a floured surface, roll the dough out to a thickness of 2/8 inch. Using a cookie cutter, cut the dough into whatever shapes you would like.
Place cookies on the baking sheet and bake for 8-10 minutes.